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Pattern rate is not at 4000 Hz

Aamir Abbasi
Intellectual 445 points
Other Parts Discussed in Thread: DLPLCR4500EVM

Hey,

There are two options in the Timing tab of the GUI. The first one is called Pattern Exposure(us) which is the amount of time for which a pattern will be displayed and the second one is called Pattern Period(us), this the interval between two subsequent patterns.

Now, I am using DLP LightCrafter 4500 and in that, Patten Exposure cannot be less than 235us and the difference between Pattern Period - Patten Exposure cannot be below 230 us. So I don't know what do you mean by exposure time = 0.

Now, I am playing a sequence of 24 1-bit images stored in flash. My Pattern Exposure is 235us and Pattern Period is 235us. I am using only one buffer so, Buffer Rotate Overhead is not valid. Now, if I put my values in the formula provided for the Pattern Rate I get 2127.65 Hz.

Pattern Rate = 1/((Exposure Time = 235) + (Bit Plane Load Time = 235) +( Buffer Rotate Overhead = 0)),
Therefore, Pattern Rate = 2127.65.

So how are you saying that DLP LightCrafter can project pre-loaded patterns at 4KHz. Kindly explain.

Thanks,
Aamir

  • 0
    TI__Intellectual 1415 points

    Hi Aamir,

    I believe you are taking the pattern rate equation from the DLPLIGHTCRAFTER and attempting to use it to compute the pattern rate for the DLPLCR4500EVM?

    If so, then there are a few things to clear up:

    • 'Bit Plane Load Time' as referred to in the LightCrafter User's Guide actually refers to the image load time to load a full image which includes 24 bit planes of data. Therefore, this item is only applicable in the LightCrafter 4500 when using more than 48 patterns, and the LightCrafter when using more than 96 patterns so that new images are required to be loaded into the buffer during the pattern sequence.
    • Pattern Period designates the period between the beginning of pattern N exposure and the beginning of pattern N+1 exposure. It is not the time between the end of pattern N's exposure and the beginning of pattern N+1's exposure.
    • The (Pattern Period - Patten Exposure) limitation is that it must be either >230µs, or = 0.

    Therefore, the maximum binary pattern rate for the LightCrafter and the LightCrafter 4500 are:

    • LightCrafter, ≤24 patterns: = 1/(250µs minimum exposure period) = 4000Hz
    • LightCrafter 4500, ≤48 patterns: = 1/(235µs minimum exposure period) = 4225Hz